Erasing the old iMac

TidBITS Talk
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I have FileVault enabled for my 2017 5K 27-inch iMac, which is on Mojave.

Are the steps listed in What to do before you sell, give away, trade in, or recycle your Mac - Apple Support sufficient to wipe the SSD securely? Is there anything else I should do?

Thanks!

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Does it just have an SSD or is it a Fusion Drive?

You can’t use Erase All Content and Settings on this iMac, so the procedure, as documented in your link, would be to restart in Recovery and use Disk Utility to erase the drive. Whether you need to reinstall macOS depends on what you plan to do with it.

There used to be options for how hard you want to erase it, but Apple removed this option for all drive types, because it was hard on SSDs. Since you’re using FileVault, a light erasure is sufficient. You could also just not erase it at all.

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Thanks! It’s just a plain SSD. Fusion drives just seemed like a gimmick with too many possible complications.

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If you plan on restore the contents of your drive to your upcoming Mac mini, I suggest making a Time Machine backup and an independent backup using Carbon Copy Cloner, SuperDuper, or just plain old Disk Utility, assuming you have sufficient external storage.

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Absolutely! I’ve never used Time Machine (its approach always seemed too fussy), but I do have multiple independent backups.

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If you erase with Disk Utility, yes. If you use the command-line diskutil command, you still have those options. If you’re worried, you can do a diskutil secureErase at level 0 - writing zeros to every disk block. Or maybe use level 1 - writing random data to every block. Do not bother with any higher-level secure erase - they will take a lot of time, won’t really make the erasure any more secure, and will put a lot of unnecessary wear on the SSD.

But even that may not be necessary. If the device supports TRIM (as all of Apple’s SSDs do), then simply deleting the system partitions and reinstalling macOS (from a bootable installer or via Internet recovery) will be fine. TRIM will mark the entire partition as garbage as a part of deleting it. Yes, the blocks might not actually be erased for some time afterward, but the data won’t be accessible without massive amounts of hackery, and even then the attacker would only get encrypted data, since this SSD was using FileVault.